Abstract

The EU HeliNOVI project was designed to improve the understanding of Tail Rotor (TR) noise reduction and vibration reduction technology by means of a comprehensive investigation of Main Rotor (MR)/TR interaction noise and rotor induced vibrations through both theory and experiment. Several tail rotor noise reduction techniques were investigated both through wind tunnel testing and through simulations. The investigation included tip speed reduction, the sense of TR rotational direction and different TR rotor position. Both the test and simulation results indicate that tail rotor noise is most important for climb and high-speed level flight. The analysis of the tail rotor noise reduction benefits from test and simulation results show that besides a reduction of rotor tip speed, the most efficient tail rotor noise reduction concept consists in changing the tail rotor sense of rotation from 'Advancing Side Down-ASD' to 'Advancing Side Up-ASU'. In addition, the noise reduction for new TR posi-tion is mainly due to increasing the advancing blade distance rather than changing TR aero-dynamic behavior.